This invention relates generally to medication infusion pumps for controlled delivery of a selected medication to a patient over an extended period of time. More particularly, this invention relates to an improved medication infusion pump of the constant flow type, for administration of the selected medication to the patient on a substantially constant flow basis. In the preferred form, the medication infusion pump of the present invention is adapted for implantation directly into the body of the patient, and for periodic transcutaneous refilling of a medication chamber within the pump.
Medication infusion pumps are generally known in the art for use in delivering a selected medication to a patient including humans and other animals in accordance with an administration schedule which can be preselected or, in some instances, preprogrammed. In recent years, such infusion pumps have been developed in compact form adapted for direct implantation into the body of a patient, to deliver a specific medication such as insulin to the patient in controlled doses over an extended period of time. An implantable infusion pump of this general type includes an internal medication chamber for receiving and storing a supply of the selected medication in liquid form. In some forms, the medication is delivered from the medication chamber into the body of the patient by a miniature pump operated by associated programmable control means for delivering the medication to the patient in selected doses at selected times. For one example of a medication infusion pump of this type, see U.S. Pat. No. 4,573,994 (Fischell). In other designs, the medication is maintained within the medication chamber defined by a metal bellows under a positive pressure for delivery as a substantially continuous and preferably constant flow through an appropriate restriction such as a capillary tube. For examples of infusion pumps which use such a positive pressure system with a capillary tube for continuous flow delivery of medication, see U.S. Pat. Nos. 3,731,681 (Blackshear), and 3,951,147(Tucker).
The present invention is directed to an improved implantable flow infusion pump of the constant flow type, wherein the pump components are arranged and assembled in a highly compact geometry that is compatible with cost-efficient manufacture, and which further provides accurate and reliable delivery of the medication over an extended period of time. The improved infusion pump is particularly designed to provide a substantially optimized and low profile housing configuration suited for implantation into the patient. Moreover, the pump incorporates an improved capillary tube and related mounting arrangement in association with a filter of substantially maximized surface area, to result in a capillary tube and filter package that resists clogging. Such resistance to clogging is especially significant when the pump is used to deliver complex protein-based medications, such as insulin, which tend to develop particulate aggregates along fluid flow paths.